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Discovered: August 16, 2007
Updated: August 24, 2007 8:56:23 PM
Also Known As: [McAfee], Troj/Bancos-BDR [Sophos], Spy-Agent.cj.gen.h [McAfee], Troj/Zbot-F [Sophos], Troj/Agent-HEF [Sophos], Troj/Zbot-AB [Sophos], Troj/Agent-HFZ [Sophos]
Type: Trojan
Infection Length: 153,600 bytes
Systems Affected: Windows

Infostealer.Monstres is a Trojan horse that may steal sensitive information from the compromised computer. It also accesses the Web site and steals personal information from resumes posted in the site.

More information on this threat can be found in the following articles:

Antivirus Protection Dates

  • Initial Rapid Release version August 16, 2007 revision 032
  • Latest Rapid Release version May 07, 2019 revision 006
  • Initial Daily Certified version August 17, 2007 revision 002
  • Latest Daily Certified version May 07, 2019 revision 008
  • Initial Weekly Certified release date August 22, 2007

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Technical Description

When the Trojan is executed, it creates the following mutex to ensure that only one copy of the threat is running on the computer:

It checks for the presence of the following firewall programs:

Next, the Trojan copies itself to the following location and appends a random amount of data to the file in order to have a random size:

It creates the following folder with system and hidden attributes:

The Trojan then creates the following files, the first of which is used to save gathered information and the second is used to store the encrypted configuration of the Trojan:

  • %System%\wsnpoem\audio.dll
  • %System%\wsnpoem\video.dll

Next, the Trojan creates the following registry entry:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\"pathx" = [MALWARE_ORIGINAL_FILENAME]

It also modifies the following registry entry so that it executes whenever Windows starts:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\"Userinit" = "%System%\userinit.exe, %System%\ntos.exe"

Next, it injects malicious code into the following running processes:

It attempts to create a malicious thread in all running processes except for the following one:

The Trojan creates some of the following mutexes to synchronize all active threads while running in memory:
  • __SYSTEM__23D80F10__
  • __SYSTEM__45A2F601__
  • __SYSTEM__7F4523E5__
  • __SYSTEM__91C38905__
  • __SYSTEM__64AD0625__

The injected code will prevent the removal of the Trojan by blocking access and deletion of all of the malicious files and by regenerating all of the registry subkeys associated with the Trojan when they are deleted.

Next, it may add the following registry entries as infection markers for the compromised computer:
HKEY_LOCAL_MACHINE\Software\microsoft\windows nt\currentversion\network\"UID" = "[COMPUTERNAME]_[UNIQUE_ID]"

It then hooks the following system functions of NTDLL.DLL using rootkit techniques to ensure that its code gets injected into each process:
  • NtCreateThread
  • LdrLoadDll
  • LdrGetProcedureAddress

The Trojan attempts to hook the following functions in the WININET.DLL library to have control of network functionalities and to steal sensitive information:
  • HttpSendRequestW
  • HttpSendRequestA
  • HttpSendRequestExW
  • HttpSendRequestExA
  • InternetReadFile
  • InternetReadFileExW
  • InternetReadFileExA
  • InternetQueryDataAvailable
  • InternetCloseHandle

It attempts to hook the following functions in the WS2_32.DLL and WSOCK32.DLL libraries to have control of network functionalities and to steal sensitive information:
  • send
  • sendto
  • closesocket
  • WSASend
  • WSASendTo

The Trojan may perform the following actions when visiting the Web sites:
  • Intercept network traffic
  • Redirect traffic
  • Steal sensitive data

The Trojan can steal sensitive information from the Web site by using an employer/recruiter account which is provided by an attacker. It downloads the details for the account from the following location:
http://[REMOTE SERVER]/mnstr/grabv2.php?getid=1

Next, the Trojan logs in to the following Web sites using the provided account:

It then searches for all available resumes, stealing the following information from each resume:
  • Name
  • Email address
  • Home address
  • Mobile and home phone numbers

Next, it attempts to post the stolen information to the following Web site:
http://[REMOTE SERVER]/grabv2.php

The Trojan may contact the following site to get instructions for spam and additional configuration information:

It sends spam email and attempts to contact the following SMTP server:


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.


The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Run a full system scan.
  4. Delete any values added to the registry.

For specific details on each of these steps, read the following instructions.

1. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:

Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, reenable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article: Antivirus Tools Cannot Clean Infected Files in the _Restore Folder (Article ID: Q263455).

2. To update the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Running LiveUpdate, which is the easiest way to obtain virus definitions.

    If you use Norton AntiVirus 2006, Symantec AntiVirus Corporate Edition 10.0, or newer products, LiveUpdate definitions are updated daily. These products include newer technology.

    If you use Norton AntiVirus 2005, Symantec AntiVirus Corporate Edition 9.0, or earlier products, LiveUpdate definitions are updated weekly. The exception is major outbreaks, when definitions are updated more often.

  • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted daily. You should download the definitions from the Symantec Security Response Web site and manually install them.

The latest Intelligent Updater virus definitions can be obtained here: Intelligent Updater virus definitions . For detailed instructions read the document: How to update virus definition files using the Intelligent Updater .

3. To run a full system scan
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.

    For Norton AntiVirus consumer products: Read the document: How to configure Norton AntiVirus to scan all files.

    For Symantec AntiVirus Enterprise products: Read the document: How to verify that a Symantec Corporate antivirus product is set to scan all files.

  2. Run a full system scan.
  3. If any files are detected, follow the instructions displayed by your antivirus program.
Important: If you are unable to start your Symantec antivirus product or the product reports that it cannot delete a detected file, you may need to stop the risk from running in order to remove it. To do this, run the scan in Safe mode. For instructions, read the document, How to start the computer in Safe Mode . Once you have restarted in Safe mode, run the scan again.
After the files are deleted, restart the computer in Normal mode and proceed with the next section.

Warning messages may be displayed when the computer is restarted, since the threat may not be fully removed at this point. You can ignore these messages and click OK. These messages will not appear when the computer is restarted after the removal instructions have been fully completed. The messages displayed may be similar to the following:

Title: [FILE PATH]
Message body: Windows cannot find [FILE NAME]. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search.

4. To delete the value from the registry
Important: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified subkeys only. For instructions refer to the document: How to make a backup of the Windows registry .
  1. Click Start > Run.
  2. Type regedit
  3. Click OK.

    Note: If the registry editor fails to open the threat may have modified the registry to prevent access to the registry editor. Security Response has developed a tool to resolve this problem. Download and run this tool, and then continue with the removal.
  4. Navigate to and delete the following entries:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Network\"UID" = [COMPUTERNAME]_[UNIQUE_ID]
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\"pathx" = [MALWARE_ORIGINAL_FILENAME]
  5. Restore the following registry entries to their original values, if required:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\"Userinit" = "%SYSTEM%\userinit.exe, %System%\ntos.exe"
  6. Exit the Registry Editor.

Writeup By: Elia Florio